Generally, there may be a liquid crystal display (LCD), a plasma display panel (PDP) and the like as conventional large scale display device.
Different from a self-luminous type PDP that is, an LCD that is not self-luminous requires a light unit.
Such a light unit used in the LCD may be categorized into an edge light unit and a direct light, based on location of light sources. In the edge type, light sources are arranged on right and left edges or up and down edges of an LCD panel. Lights may be dispersed a front region uniformly, using a light guide plate. Accordingly, the edge light unit has good luminous uniformity and it may enable the panel ultra-thin.
The direct light unit is used for a 20-inch-or-more display. In the direct light unit, light sources are arranged on a backside of a panel. Accordingly, the direct light unit has an advantage of better luminous efficiency than the edge light unit and it is usually used for a large scale display that requires high brightness.
A cold cathode fluorescent lamp (CCFL) is used for the light source of the conventional edge or direct light unit.
However, an electric voltage is applied to the light unit using the CCFL constantly and quite an amount of electricity is used disadvantageously. Also, the CCFL has a disadvantage of approximately 70% of color reproduction, compared with a cathode-ray tube (CRT) and another disadvantage of environmental pollution because of mercury added thereto.
To solve such disadvantages, there have been actively in progress studies on a light unit using a light emitting diode (LED) as a substitute for the CCFL.
In case of using the LED for the light unit, a partial on/off of LED arrays may be enabled and power consumption may be reduced remarkably. A RGB LED exceeds 100% of color production specifications of National Television System Committee (NTSC) and a more vivid image quality may be provided to a consumer.